A team from the University of South Florida returned from a six-week Antarctic expedition with samples of sea squirts whose bacterial toxins have killed melanoma cells in mice. The expedition included the Desert Research Institute and the Scripps Institution of Oceanography. The National Science Foundation funded it.
The samples are ascidians, invertebrates known as sea squirts. They thrive in icy Antarctic waters and produce bacterial toxins as protection against predators. Bill Baker, professor of chemistry at USF, said the toxins can be repurposed. Research already completed by his team showed the toxin killed melanoma cells in mice without killing the mice.
Baker said the good news is that the treatment did not kill the mice, and it did kill their cancer. That shows the toxin has physiological properties to act like a drug. He said the team needs grams of material for a bigger study in mice, then possibly other animal models. If safety can be proven, human trials could begin.
Baker acknowledged the pathway to an approved anti-melanoma drug is long. It would need a sequence of tightly regulated trials, each larger than the last, even after a drug was formulated. The knowledge gained from the expedition could significantly advance the timeline.
Divers worked under ice and leopard seal pressure
Teams of divers descended to depths of up to 130 feet for about half an hour at a time. Ben Meister, a USF diving safety officer for the expedition, said sea temperatures were only one challenge. The team also dealt with ice, leopard seals, changing seas and sometimes very limited visibility. Every dive had to be carefully planned to balance getting the work done while keeping everyone safe.
The expedition's lead researcher, Alison Murray of the Desert Research Institute, collected samples. The fieldwork advanced understanding of how the melanoma-killing bacterium lives inside the ascidian, and the ecological relationship between the bacterium and the organism. Baker said lessons from the field studies will help when the team starts animal models and human models, and will give a better idea of what to do and what not to do in using the toxin as a drug.
The researchers returned exhausted, but excited about the laboratory stage. That stage will include trying to synthetically reproduce the toxin.
The next step is making the toxin in a lab
Baker said the team needs hundreds of milligrams to grams of the metabolite. A basketball-size collection of ascidians might yield one-thousandth of that amount. He said the team cannot collect 1,000 basketball quantities from the Antarctic, because that would destroy the ecology. The alternative is to figure out how to make the substance in the lab.
Baker started his career in marine biology and chemistry in 1990. He has worked on many projects evaluating undersea organisms for possible use in prevention and treatment. He noted that more than half of Food and Drug Administration-approved drugs originate from natural sources. He also cited other metabolites found in sponges, corals, tunicates and other organisms, not only in Antarctica.
Baker called the melanoma discovery a career high point. He said killing cancer cells in a petri dish is one thing, and going beyond that is much harder. The team has cleared some of the higher hurdles, and now has to make the next one.
For travelers planning an Antarctic voyage, the question worth putting to an operator is whether a sailing includes a research or science component and how the team coordinates with scientists working in the same waters. The sea squirt study is a reminder that Antarctic waters are active research sites, not scenery alone.